Aggregation-dependence of Optical Properties and Fluorescence Quenching of a Water-soluble Poly（phenylene ethynylene）

In recent years, water-soluble conjugated polymers have been attained much attention as the optical platform in fluorescent chemical and biological sensors1. In comparison to the small molecule counterparts, conjugated polymers exhibit signal amplificatio…     

Optimized design of laser range finding system using the self-mixing effect in a single-mode VCSEL

An optimized design of laser range finding system using the self-mixing effect in a single-mode verticalcavity surface-emitting laser (VCSEL) is proposed. In order to improve the ranging accuracy and expand dynamic measurement range, we apply difference frequency analog phase-locked loop (PLL) instead of fast Fourier transform (FFT) to process signal, and choose the optimum triangular wave frequency fm= 500Hz and small modulation current △Ip-p = 0.28 mA to modulate single-mode VCSEL. The experiment results show that, without controlling the laser's temperature, the ranging accuracy is better than 2 mm and the measurement dynamic range is as large as 50-500 mm when the sampling time is 0.1 s and the room temperature is 0-55 ℃.     

应用强度差压缩光进行微弱吸收光谱学测量

提出一种应用强度差压缩态光场进行灵敏度吸收光谱的分析的方案，并通过并经典理论分析证明，该方案的测量灵敏度不受真空起伏限制，最小可测吸收系数低于光波场的散粒噪声极限。     

在热压缩态中测量相位算符的涨落

利用热场动力学的方法计算了热压缩态中测量相位算符的涨落，引入了两种类型的基础量子涨落，一种是与测量相位的两个正交分量相联系，另一种是与一个测量相位分量和光子数相联系。由此，研究了热压缩压中测量相位涨落的两种压缩及其与温度的关系。     

被动控制装置改进轴流风机失速余度的实验研究

1前言近年来，使用被动控制装置改进风机的失速特性一直引起风机设计和研究人员的重视。例如：在转子前加装可调进口导叶，在转子叶尖区吹气和放气，机匣处理装置（轴向、斜向和周向开缝）等来抑制风机失速的技术已被实际应用。但这些装置仍然存在着一些缺点。例如：降低了风机的最高效率尚2％－4％），改进失速余度的范围小，大约只有20％的流量失速金度的改进．以及装置本身结构复杂，增加了造价。因而一种被称为空气分流器的被动控制技术，首先由NBAHOB；C．K申请了专利川。由于空气分流器在控制轴流风机失速有很好的效果，因而许多…     

The subgroups of the special linear group over a skew field that contain the group of diagonal matrices

For any (noncommutative) skew field T, the lattice of subgroups of the special linear group Λ=SL(n,T) that contain the subgroup Δ=SD(n,T) of diagonal matrices (with Dieudonné determinants equal to 1) is studied. It is established that for any subgroup H, Δ≤H≤Λ, there exists a uniquely determined unital net σ such that Λ(σ)≤H≤N(σ), where Λ(σ) is the net subgroup associated with the net σ and N(σ) is its normalizer in Λ. Bibliography: 11 titles. Published inZapiski Nauchnykh Seminarov POMI, Vol. 211, 1994, pp. 91–103. Translated by Bui Xuan Hai.     

Seismic response of underwater members of variable cross section

This paper is concerned with a method for solving seismic response problems of a pile of variable cross section with a tip inertia subjected to a sea bottom seismic displacement. The analysis developed here is based on an elastodynamic theory in which the effects of the continuously distributed mass and rigidity of the pile are included. The method includes use of Fourier series expansion, the Laplace transform, the transfer matrix method and the residue theorem in order to deal with the complex seismic displacement and arbitrarily shaped piles; considerable simplification of the calculations is thus achieved. The theoretical results given are applicable to seismic response problems for a pile of arbitrary shape with a tip inertia, excited by arbitrary displacements. As an application of the present theoretical results, the dynamic response has been calculated for hollow piles of curved conical shape with tip inertias and double taper beams subjected to seismic displacements.     

Ccontrolling the Transition Between "Higher" and "Lower" State of OB in Coherent Atomic Medium

We present a new experimental demonstration that the threshold points and shape of OB hysteresis curve in a four-level Rb atomic system inside an optical cavity were controllably changed by optical signals.Tuning the triggering optical signal to two different transitions of the atomic system we found that the OB threshold points shift toward different direction and at the same time the shape of the OB curve is also changed.For a given intensity of probe laser the OB system can be reliably inversed from its lower stable state to upper state under the triggering of a suitably tuned optical pulse signal (we named it up-controlling signal).More interesting, the inversed OB state does not drop to its initial lower stable state after the triggering pulse signal has passed, but moves to the upper branch of the initial OB curve and stably stays there until another optical signal tuned on other atomic transition (named down-controlling signal) coming.The result shows that there is the ability of information storage in the OB system.The experiments are reasonably explained with the change of cavity resonant condition resulting from the enhanced third-order nonlinearity in multilevel atomic system owing to atomic coherence.     

Spin-polarized current produced by a double barrier resonant tunneling diode

The spin-polarized tunneling current through a double barrier resonant tunneling diode (RTD) made with a semimagnetic semiconductor is studied theoretically. The calculated spin-polarized current and polarization degree are in agreement with recent experimental results. It is predicted that the polarization degree can be modulated continuously from +1 to −1 by changing the external voltage such that the quasi-confined spin-up and spin-down energy levels shift downwards from the Fermi level to the bottom of the conduction band. The RTD with low potential barrier or the tunneling through the second quasi-confined state produces larger spin-polarized current. Furthermore a higher magnetic field enhances the polarization degree of the tunneling current.     

Copolymerization of Ethylene/1-Butene with Heterogeneous TiCl4/(α-Diimine)nickel(Ⅱ) Complex Combined Catalyst

The new type heterogeneous combined catalyst system TiCl4-(α-diimine)nickel(Ⅱ) complexes/MgCl2-SiO2/AlR3 was prepared. Ethylene and 1-butene were copolymerized with the catalysts in slurry phase. It was found that with combined catalyst, the copolymers with lower density and higher branched degree were obtained. 13CNMR results showed that in the obtained copolymers existed not only ethyl but also some other kinds of branches due to the fact that ethylene exhibits the behavior of oligomerization and copolymerization in-situ with combined catalysts.